Rubiscolytics: fate of Rubisco after its enzymatic function in a cell is terminated

Abstract

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the predominant protein in photosynthesizing plant parts and the most abundant protein on earth. Amino acids deriving from its net degradation during senescence are transported to sinks (e.g. developing leaves, fruits). Rubisco catabolism is not controlled only by the overall sink demand. An accumulation of carbohydrates may also accelerate senescence and Rubisco degradation under certain conditions. Amino acids produced by proteolysis are rapidly redistributed in plants with proper source-sink relationships. In leaves of wheat plants with reduced sink capacity (e.g. sink removal, phloem interruption by steam girdling at the leaf base), Rubisco is degraded and free amino acids accumulate. They may be washed out in the rain during late senescence. In leaves of depodded soybeans, Rubisco is degraded and amino acids can be reutilized in these leaves for the synthesis of special vacuolar proteins in the paraveinal mesophyll (vegetative storage proteins). Nitrogen deriving from Rubisco degradation in older (senescing) leaves of annual crops is integrated to some extent again in newly synthesized Rubisco in younger leaves or photosynthesizing tissues of fruits. Finally, a high percentage of this nitrogen is accumulated in protein bodies (storage proteins). At the subcellular level, Rubisco can be degraded in intact chloroplasts. Reactive oxygen species may directly cleave the large subunit or modify it to become more susceptible to proteolysis. A metalloendopeptidase may play an important role in Rubisco degradation within intact chloroplasts. Additionally, the involvement of vacuolar endopeptidase(s) in Rubisco catabolism (at least under certain conditions) was postulated by various laboratories.

Organic reactions for the electrochemical and photochemical production of chemical fuels from CO2 – The reduction chemistry of carboxylic acids and derivatives as bent CO2 surrogates

“…RuBisCo -(Ribulose-1,5-BISphosphate Carboxylase/Oxygenase) is the enzyme responsible for the carbon fixation mechanism as described in Scheme 3. RuBisCo is believed to be the most abundant protein on Earth [20,21].…”

“…The adduct has been shown to be able to undergo sequential reductions by a terminal reducing agent, a silane. Intermediate formates (20) and silanols (21) have been observed by mass spectrometry (see Scheme 5).…”

Mobilization of Rubisco and Stroma-Localized Fluorescent Proteins of Chloroplasts to the Vacuole by anATGGene-Dependent Autophagic Process

“…In addition, these proteins are also degraded under carbon-limited conditions, which are caused by darkness (Wittenbach, 1978), and their carbon is used mainly as substrates of respiration. Despite its important function to allow nutrient recycling, the degradation mechanism is not clearly understood yet (for review, see Krupinska, 2006;Feller et al, 2008).…”

Delayed expression of SAGs correlates with longevity in CMS wheat plants compared to its fertile plants

“…In soyabean also leaf N and rubisco protein content declined faster in plants with sinks compared to de-sinked plants (Crafts-Brandner and Egli 1987). A net degradation of rubisco and other chloroplast proteins can be observed during endogenously initiated leaf senescence as well as during or after abiotic stresses which allows the reutilization of N in other organs (Feller et al 2008). During early stages of senescence, rubisco accounts for about 90 % of the degraded proteins (Miller and Huffaker 1985).…”

“…However, the equilibrium between production and scavenging of ROS may be perturbed during senescence as the activity of stromal and thylakoidal SOD and APX declined during senescence in wheat . High ROS accumulation in chloroplasts resulted in protein oxidation and degradation especially of large subunit of rubisco (Feller et al 2008).…”